Process for producing alkylsubstituted acylamides



Jan. 26, 1954 c. DowNlNG 2,667,511

PROCESS FOR PRODUCING ALKYL-SUBSTITUTED ACYLAMIDES Filed Aug. 25, 1951 BYvM @im Patented Jan. 26, 1954 UNITED STATES PATENT OFFICE PROCESS' FOR PRODUCING ALKYL- SUBSTITUTED ACYLAMIDES Gole Downing', Decatur, Ala.,l assigner, by mesne as siggnments` to The Chemstrand Corporation, a., corporation of Delaware Application August 25, 1951, Serial No. 243,685

proceeds.

The production of dimethyl acylamides is described in an article by Ruhof and Reid entitled A Series of Aliphatic Dirnethylamides 59 JACS 401 (1937).

According to these authors the dimethyl acylvamides are prepared by the reaction of a carboxylic acid and dimethylaminc and the products are recovered from the reaction mixtureA as an azeotrope which boils uniformlyA 4 to 5 C. above the boilingv points of the pure acylamid'es. The boiling points and compositions of the azeotropes occurring in this system are identified by these authors, as follows.:

result of the occurrence. of theY abovev azeotropes it is dinicult to. p .urif-y these compounds.

`As a matter of fact, the4 existence. of the above and butyric acid or the corresponding anhydrdes. -to a bedr Comprising dimethyl aevlarnde andthe 'correspondingaed. in. Wh

eh; bed-v the proportion er the eeid. is less than that corresponding to; the azeotrope thereof.

The reaction occurring in? the process; when em.- ploync acetic acid may be. Written as. follows.:

CHBCOOHJF. (CH3) mia-:..cnscomcno zJr-izo.-

the reaction requiring one mole of acetic acid to one mole of dimethylamine and producing 'one mole of dimethyl aeetamide together with one mole of water.4

When. working with` the corresponding anhydride the reaction is as follows:

wherein onev mole of acetic anhydride is reacted with two moles of dimethylamine to form one ,mole of acylamide and one mole of water.. Itgis,

of course, apparentthat the water serves tohydrolyze the acid anhydrideto the acid.

While ordinarilyr the stoichiometric proportions of dimethylamine to acidy or anhydride are as indicated by the equations written above, I have found that the proportions of dimethylarnine with respect to acid and/or acid anhydride may be advantageously maintained so asI to afford somewhat of an excess thereof over the eX-act stoichiometric proportions. The excess amine which is not reacted is not lost, since-the pres-ent process provides a novel method. by which suhstantialiy all of the amine is retained in the ET QQ- ess.

The process of the invention will be apparent from the following description when, read inl connection With the drawing, the single ligure of which illustrates diagrammatically an assembly of apparatus suitable for carryingout the process. In the following description the process, is described as applied to the preparation of N,N=di

methyl acetamide from acetic acid and dimethylamine. However, it is apparent that the, same process may be carried out for any of the other dimethylacylamides. herein disclosed.

In the drawing, It indicates a tank containing glacial acetic acid, Il a pipe for conveying the same to a packed scrubber I2, through which it flows leaving the same by pipe I3 and then flowing into reactor I4. f Numeral I5 indicates a tank containing dimethylamine. A pipe I6 connects this tank with reactor I4 permitting the dimethylamine to flow thereto. it is preferred to vaporize the dimethylamine prior to introduction into the reactor. Reactor Id is provided with a stirrer and also with steam coils which arel not-shown; However, the coils are connected to a steam source, 'Ilvvhera by the, contents of the reactor maybe heated to the boiling point d vapor conductor I8: cou.-

nects with packed tower I9, the latter in turn being provided with a vapor pipe 29. The upper end of the packed tower I9 is connected by pipe 20 with water-cooled condenser 2|, the liquid condensate forming therein owing by pipe 22 to pump 23. The discharge of the pump flows by pipe 24 to pipes 25 and 26, the former connecting with the upper part of packed tower I9 and the latter pipe with still 21. denser 2| is connected by pipe 28 with the lower part of scrubber I2, the upper part of the latter being connected to condenser 36 and then vented by pipe 31. Still 21, which serves as a light ends column, is provided with a steam coil supplied with steam by pipe 3B, a vent 2| and a product discharge 32.

Example 1 In carrying out my process in the above-described apparatus, reactor I4 is first lled approximately one-half full with a mixture of dimethyl acetamide and acetic acid, the content of acetic acid being below that present in the azeotrope. A convenient composition to be employed in reactor I4 consists of a mixture of 88% of dimethyl acetamide and 12% of acetic acid.

The mixture of dimethyl acetamide and acetic acid in reactor I4 is heated to the boiling point (162-l65 C.) while a supply of acetic acid'from tank IIJ is introduced via pipe II,'scrubber I2 and pipe I3, the acid preferably being introduced below the level of the liquid in reactor I4. At the same time a stream of dimethylamine from tank l5 is passed into reactor I4 via pipe I6. The amount of dimethylamine is supplied in excess of the stoichiometric proportion of dimethylamine entering by pipe I3, however it is substantially equivalent to the acetic acid entering the system by pipe I I.

'I'he vaporized reaction product formed in the reactor passes out by pipe I8 into packed tower I9 and then passes by pipe 20 into condenser 2| where most of the product is condensed. The condensateleaves the condenser by pipe 22 and then by pump 23 a part thereof is returned to packed tower I9 by pipe 25. The condensate so returned serves as reiiux therein, ultimately returning to reactor I4 by pipe 34. The uncondensed vapor leaving condenser 2| by pipe 28 and consisting largely 'of unreacted dimethylamine passes into scrubber I2 where it is absorbed by the acetic acid therein.

Scrubber I2 is maintained at a temperature somewhat above 150 C. and preferably below V165 C. This temperature is maintained by the heat of reaction between the dimethylamine entering by pipe 28 and acetic acid supplied by pipe I I. For starting up purposes only, heat may be supplied to scrubber I2 by passing steam into the scrubber by pipe 35 or a heating jacket may beY provided for accomplishing the same purpose. Such heating means may also be useful when excessive heat loss occurs from the scrubber. When the process is operated as herein-described, approximately 60% of the reaction forming the acylamides takes place in scrubber I2, with the balance taking place in reactor I4 and in tower I9.

It has been found that commercial dimethylamine contains small amounts of impurities such as monoand tri-methylamine together with varying amounts of inerts. The trimethylamine and the inerts are not reacted with the acid, hence they are vented from the system by means of pipe 29. This pipe leads to water-cooled condenser 36, wherein condensation and return of The upper part of conproduct to a vapor temperature of about C.

The light ends consisting of water and small amounts of dimethylamine are vented by pipe 3|. If substantial quantities of dimethylamine are vaporized at this point a separation thereof from water may be made and the dimethylamine returned to scrubber I2. The liquid product from still I4 leaving by pipe 32 flows to storage tank 33. 'I'his is the product of the process.

c Any monomethylamine present as an impurity in the dimethylamineforms the corresponding monomethyl acylamide. This product has a substantially higher boiling point than does the vdimethyl acylamide and for this reason is retained in the reactor I4. When the reactor contents have accumulated substantial amounts of the monomethyl acylamide, they are withdrawn and purified by an ordinary fractional distillation.

Example 2 d of propionic acid. After the completion of the primaryV reaction the reaction mixture is volatilized, as described in Example 1, the vapor entering the packed column and contacting reux obtained from the condenser 2|. The crude product thus obtained is then distilled to yield .substantially pure dimethyl propionalnide in good yield.

Example 3 Eighty-eight parts by weight of butyric acid and 50 parts of dimethylamine are continuously charged to the system comprising scrubber I2, and reactor I4 connected to packed tower I9 and condenser 2|, as described in Example 1. The reactor contains a previously prepared mixture of 66 parts by weight of dimethylbutyramide and 16 parts of butyric acid. After the completion of the primary reaction the reaction mixture is volatilized as described in Example 1, and the vapor passed through packed tower I9 where it is connected with reflux from condenser 2| The crude. product is then distilled to give dimethylbutyramide.

I claim:

1. The method of manufacturing a dimethylacylamide of the formula:

RCCN (CH3) 2 where R is an alkyl radical having from 1 to 3 carbon atoms which comprises adding dimethylamine and an acyl compound selected from the group consisting of acetic acid, propionic acid, butyric acid and the corresponding anhydrides thereof to a body of liquid comprising dimethylacylamide and the corresponding acid containing the acyl radical of the desired acylamide, the proportion of said acid with respect to said dimethylacylamide present in said body being less than that corresponding to the azeotrope thereof.

2. The method of manufacturing a dimethylacylamide of the formula:

RCON(CH3) z where R is an alkyl radical having from 1 to 3 carbon atoms which comprises adding dimethylamine and an acyl compound selected from the group consisting of acetic acid, propionic acid, butyric acid and the corresponding anhydrides thereof in such proportion that the dimethylamine is at least equal to the stoichiometric proportion required by the reaction, to a body of liquid comprising dimethylacylamide and the corresponding acid containing the acyl radical of the desired acylamide, in which body the proportion of said acid with respect to said climethylacylamide is less than that corresponding to the azeotrope thereof.

3. The method of manufacturing dimethylacetamide which comprises introducing dimethylamine and acetic acid to a body of liquid comprising dimethylacetamide and acetic acid, the proportion of acetic acid in said body being less than 21.1% by Weight.

4. The method of manufacturing dimethylacetamide which comprises introducing dimethylamine and acetic anhydride to a body of liquid comprising dimethylacetamide and acetic acid, the proportion of acetic acid in said body being less than 21.1 by weight.

5. The method of manufacturing dimethylacetamide which comprises introducing dimethylamine and acetic acid in such proportion that the dimethylamine is at least equal to the stoichiometric proportion required by the reaction to a body of liquid comprising dimethylacetamide and acetic acid, in which body the concentration of said acid based on said dimethylacetamide and acetic acid is less than 21.1% by Weight.

6. The method of manufacturing dimethylpropionamide which comprises introducing dimethylamine and propionic acid to a body of liquid comprising dimethylpropionamide and propionic acid, the proportion of propionic acid in said body being less than 23.4% by weight.

7. The method of manufacturing dimethylpropionamide which comprises introducing dimethylamine and propionic acid in such proportion that the dimethylamine is at least equal to the stoichiometric proportion required by the reaction to a body of liquid comprising dimethylpropionamide and propionic acid, in which body the concentration of said acid based on said dimethylpropionamide and propionic acid is less than 23.4% by weight.

8. The method of manufacturing dimethylbutyramide which comprises introducing dimethylamine and butyric acid to a body of liquid comprising dimethylbutyramide and butyric acid, the proportion of butyric acid in said body being less than 32% by Weight.

9. The method of manufacturing dimethylbutyramide which comprises introducing dimethylamine and butyric acid in such proportions that the dimethylamine is at least equal to the stoichiometric proportion required by the reaction to a body of liquid comprising dimethylbutyramide and butyric acid, in which body the concentration of said acid based on said dimethylbutyramide and butyric acid is less than 32% by Weight.

10. A method for manufacturing a dimethylacylamide of the formula:

RCON(CH3) 2 wherein R is an alkyl radical having from one to 3 carbon atoms, which comprises adding dimethylamine and an acyl compound selected from the group consisting of acetic acid, propionic acid, butyric acid and the corresponding anhydrides thereof to a body of liquid in a reaction zone comprising dimethylacylamide and the corresponding acid containing the acyl radical of the desired acylamide, the proportion of said acid With respect to said dimethylacylamide present in said body being less than that corresponding to the azetrope thereof, said body of liquid being heated to the boiling point, said acid being passed through a scrubbing zone prior to entering the reaction zone, condensing the vaporized reaction product, and returning a portion of the condensate to the reaction zone, all of said steps being maintained so that the major portion of the reaction takes place in the scrubloing zone and the balance takes place in the reaction zone.

11. A method for manufacturing dimethylacetamide which comprises adding dimethylamine and acetic acid in such proportion that the dimethylamine is at least equal to the stoichiometric proportion required by the reaction to a body of liquid in a reaction zone comprising dimethylacetamide and acetic acid, in which body the concentration of said acid based on said dimethylacetamide and acetic acid is less than 21.1% by weight, said body of liquid being heated to the boiling point, said acid being passed through a scrubbing zone at a temperature of 150 to 165 C. prior to entering the reaction zone, condensing the Vaporized reaction product, and returning a portion of the condensate to the reaction zone, all of said steps being maintained so that of the reaction takes place in the scrubbing zone and the balance takes place in the reaction zone.

COLE DOWNING.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,954,433 Thomas et al. Apr. 10, 1934 1,986,854 Reid Jan. 8, 1935 2,213,763 Gordon Sept. 3, 1940 

1. THE METHOD OF MANUFACTURING A DIMETHYLACYLAMIDE OF THE FORMULA: 